You turn off the water, open all the faucets and wait for the pipes to drain completely.

It works sometimes, but not always.

Close all the faucets, then turn the water back on.
Bleed the air at each faucet and hope.

What is your water pressure? Often water hammer will occur when pressure is too high.

By draining the system, you are allowing air back into the air chamber in your plumbing system (assuming you have one). If you know where the air chamber is located, if it was installed properly, you should be able to isolate and drain it without draining the whole system. Eventually, the water under pressure will absorb the air and the hammer will reoccur. The higher your water pressure, the faster the recurrence.

Thank you both! I have very low water pressure - on a 9 home community well. Never had a problem with this until the remodel. GC says I should install something on the washing machine lines??? I say the plumber did something wrong like a loose pipe somewhere? (didn't like or trust the plumber at all) but am trying to isolate the problem before knowing whether to insist the plumber come back and figure it out/fix it.

The problem began after you had the upstairs bathroom remodeled.

Field manufactured water hammer arrestors are simply a 12 to 18" stub of vertical pipe that is capped off at the high point in your piping system. Normally they are located inside the wall behind the tub or lavatory supply stubouts.

Sight unseen, I suspect they may have taken the original piping out and when they installed the new pipe instead of using a tee to make the lav or tub taps they used an elbow and did not recreate the vertical stubs.

You are on a multiple service well system so you may not have an expansion tank on your water heater. You could install an expansion tank at the water heater and it would not only allow for expansion, it would serve as a whole house water hammer arrestor.

You could also install hammer arrestors on your laundry lines or any readily accessible point in your piping system.

Thank you lazypup. I suspect you are correct about what they took out and didn't replace upstairs. I do not have an expansion tank. The hammer arrestors are what my gc recommended. Makes me mad to have to pay to fix what they didn't do correctly. Since the laundry lines are not a "high point" in my system will it fix the hammer for the whole house, which doesn't seem to originate at the washer (although when the water stops flowing into the machine it hammers the same place as all the other faucets)or just at the laundry? I really appreciate your help and expertise sharing.

Quick acting valves like washing machines require a water hammer arrestor.

The overall piping sounds like it may not be well fastened in place.

Okay, thanks. Since it didn't hammer before the new plumbing was added/redone, it does sound like I might have to have the plumber come back and figure it out. It hammers with any hot water valve that opens - every faucet, dishwasher and washer, too. Ugh!

"You could install an expansion tank at the water heater and it would not only allow for expansion, it would serve as a whole house water hammer arrestor."

IMHO, justalurker's advice is best. Straightforward, easy to get to, reasonably-sized, and doesn't cost much.

Thanks asolo - it does seem most practical if it will fix everything and not just the hammer at the washer. One more question. I forgot to say that we added a circulation pump for the hot water to get it to the new bath more quickly. But I found it to be too wasteful of electricity and because my schedule is erratic a timer didn't really help, so I don't use it. Any chance that could be contributing? I turned it on yesterday just to experiment and it seemed to make the hammer much worse when I had it on. Does that make sense to anyone?

Expansion tanks do not function as hammer arrestors.

Water hammer is caused by moving water coming to a sudden stop when a valve is closed (the momentum of the water is transferred to the piping).

An expansion tank at a remote location is not going to have any real affect on water hammer.

Oh contrare..An expansion tank will serve as a whole house water hammer arrestor.

Water hammer is not caused by the sudden stop of moving water because the velocity of flow is too slow to generate a significant force.

Water hammer is caused by the immediate increase in pressure from working head pressure to static head pressure when a quick acting valve is closed.

"Expansion tanks do not function as hammer arrestors."

"An expansion tank at a remote location is not going to have any real affect on water hammer."

Well, that would be news to many people....myself included. I believe you are mistaken.

"Water hammer is not caused by the sudden stop of moving water because the velocity of flow is too slow to generate a significant force. "

And the pipes all flex and jump from the pressure???

Any moving fluid has momentum, at ANY velocity.

Where do you think the energy to produce a pressure change comes from?

olychick,

if you open and then gently slowly close the tap, can you get the flow to stop without hammering?

The first response to your OP had a good idea that you can try out too, before going whole-hog. There may be one hammer arrestor somewhere, but it got filled up, and then when the power was off it partially emptied and this could be why the problem was only partially fixed.

One day, open all the pipes and let air in. (E.g. when you are away for a day. Or on vacation.) . The one hammer arrestor that is full of water will get air. If you can knock shake or vibrate the pipes a bit, it helps empty the water in them. Problem solved for X length of time.

Now, the next questions are where you want another hammer arrestor to be installed, and then, what kind of hammer arrestor. They now make cute little ones that go with your shutoff valves under the sink. These are easy to install. You have lots of options. You might not need a hammer arrestor for the next ten years if you find that the one you have already just needed to be drained once and for all.

A small expansion tank with a bladder will perform exactly the same function as an air chamber. In an air chamber there is no physical barrier between the air and the water so the air will eventually be absorbed into water and the chamber will flood, rendering it useless until you drain it again. The frequency of required draining will depend on your water pressure and water chemistry. An expansion tank, on the other hand, has a physical barrier so you will not periodically have to reintroduce air as you would with a simple air chamber. Neither, however, is optimal. The air chamber will require periodic reintroduction of air and the expansion tank takes up space. If you already have an air chamber, you can follow the advice from previous posts and see how long it takes for the water hammer to return.

The best option is a water hammer arrester. It consists of an air chamber separated from the water by a piston. It will stop the water hammer, take up very little space, and be inexpensive.

I'm learning so much thanks to all the expertise here. I appreciate you all taking your time to help.

David, if I close the valve slowly I can avoid the hammer. VERRRY slowly. I will try the draining of the system in the next week or so. Our power/water goes off here so frequently, if I am home when it happens and can remember to open all the valves while it is off, I might be able to keep ahead of it.

Honestly, it never was a problem here until this remodel and am very resentful of the plumber not doing whatever he should have...If I add a hammer arrester, do I understand correctly that I only need one someplace and it does not have to be at the peak of the plumbing system? Or do I need one at each hot water valve?

Thanks again. I'll post after I drain the system and see if it cures it. And for how long.

Typically, you want to install a hammer arrester as close to the problem valve as possible. However, since the problem happens on all hot water valves, it should be installed on the pipe between the last two fixtures in the piping. If you have a large house or complex piping, you can install at each fixture, starting with the big ones, like the clothes washer.

An arrestor is actually required near quick acting valves, but it is often ignored.

There should be one in each line at the clothes washer (electric solenoid valves are used in the washing machine) and near the dishwasher.

If the pipes are accessible in a basement you need to see if they are adequately secured in place with the correct straps.

This alone can often stop the worst of the hammering as the pipes move around when flow stops.

Single handle faucets (and 90 degree faucets) can often be turned off fast enough to need an arrestor also.

Old multi turn screw faucets usually closed slowly enough that hammer was not as much of an issue with them (it took some real effort to close them fast enough).

ditto brickeyee

Machines (clothes washer and dishwasher) are not made to close water gently. Go figure. This would be a great feature to ask for. OR, why not add a water hammer arrestor inside the machine? These days you can get water hammer arrestors that don't need to be drained. The technology does exist, and it is widely sold. I don't get it!! Why not have a water hammer arrestor inside the machines !!!

With the pipes well strapped there will be less noise but the problem has not been dealt with.

Because if you put in inside the machine and something goes wrong with it, you will have turned a $20 part into a $400 repair. Why would any consumer want that?

"Because if you put in inside the machine and something goes wrong with it, you will have turned a $20 part into a $400 repair. Why would any consumer want that?"

That argument could be used for just about anything.

If the one in the wall has something go wrong the plumber is liable to nail you for that much anyway.

No one like to spend money, especially on ho-hum things like washing machines.

No manufacturer is going to up the price to cover the parts and be at a competitive disadvantage, and they are not going to just eat the cost.

Well, I didn't read the whole thread but if you have low pressure and are getting some pipe banging I can almost guarantee its a loose pipe somewhere. Long story short I've been in my home for 15 years. Always had pipe banging whenever I would shut off a tap, regardless where it was. My pressure is about 65psi so I installed hammer arrestors everywhere. No difference at all. I also have the air gap pipes but they made no difference either.

A month ago I was replacing a bathroom faucet and noticed the pipes coming into the cabinet were loose. I could move them several inches. I checked the other water supplies and low and behold same thing, even the toilets! I took some expanding foam and sprayed it around the pipes where they enter the cabinet. I know its not ideal but I'm not removing cabinets and drywall to secure a pipe. The foam expanded, dried and essentially secured the pipes. I did this on all the pipes and my plumbing is now quiet as a church mouse. I lived with that for so long and all it took was a $5 can of Great Stuff to fix.

Tell your GC to fix it. Its his problem not yours.

Personal experience....expansion tank installed above our water heater did NOT fix the water hammer. They are not made for that purpose. The little water hammer arrestor that we put on the toilet worked like a dream....even though none of the plumbers wanted to install it. They didn't believe in it. Instead they installed anything and everything they could think of to fix the problem and still had the water hammer. Go with the little arrestors and don't pay attention to the plumbers.

I came here to post and get help with the very same problem a hammering faucet.

New kitchen faucet hammers old one did not. I have notice very intermittent burst of water what is like a big bubble in my toilet and 2 outside taps burst 2/3 times before I get water out of the hose.

Why just certain areas in the lines what causes air in the lines.

We placed a wedge to stop the line from moving it did nothing stop the hammering.

We will try some other things posted here most likely go with the arrestors.

Water hammer is a specific plumbing noise, this problems usually occurs when you shut off the water suddenly and fasting moving water rushing through the pipe is brought to a quick halt. Take the proper care of your water hammer or consult with plumber.

Here is a link that might be useful: hiblow pump

This post was edited by JeromeMoler on Thu, Aug 28, 14 at 3:32

We learned something new.....the control on your shower has a cartridge in it. Had it replaced and it cured the water hammer we had. Everyone thought it was in the wall where the shower pipes are, but one guy finally put his ear on the shower and was able to narrow it down to the sound coming from the control handle. Replaced the cartridge and no more hammer.

Other option is water hammer arrestors which really do work.